Applied Mechanics and Materials Vols. 638-640

Abstract: The factors affecting durability of concrete structures is described in This paper .It is pointed out here that is the concept of durability in prefabricated concrete structure , the influencing factors and failure mechanism in cold regions. It is proposed which are the methods and corresponding measures to enhance the durability of concrete structures.

Abstract: Different kinds of hemihydrate calcium sulfate whiskers were fabricated by calcination method under the condition of 115-600 °C. And the density, moisture rate and mechanical properties of composites of gypsum and whisker were studied. The specific strength of composites was investigated. The results show that gypsum boards with whisker calcined at 115 °C and 300 °C have the maximum and minimum densities, which are about 1658 kg/m³ and 1604 kg/m³, respectively. Hydration ability of anhydrous calcium sulfate whisker is the strongest. The values of specific strength of gypsum board reinforced by different types of whiskers suggested that the porosity of the composites changed with the different kinds of whiskers, which agreed well with the moisture rate and mechanical properties.

Abstract: Embankment stability can be improved by using good quality fill materials, applying intensive management, and constructing appropriate hydraulic structures. The good quality the fill material for a embankment in the field is the most important factor of embankment construction technology, which uses bed sediment to ensure the safety and cost effectiveness of an embankment. Also, the field compaction characteristics of poorly-graded sand (SP), distributed largely in Yi-river of China in mixing with granitic weathered soil (SW), are analyzed.

Abstract: Based on 6 testing beams in site cast, the mechanical behaviors of RC beams after reinforcement are analyzed. Concrete-replacing and grouting were used to reinforce the damaged component. When the reinforcement materials reached sufficient strength and maturity, beams were subjected to experiments of bending bearing capacity. Cracking load and ultimate bearing capacity were analyzed relatively, drawing some conclusions which could use as the reference of reinforcing concrete structure after damage.

Abstract: Steel Reinforce Concrete Beam (SRCB) has a better flexural strength and excellent performances of ductility and seismic resistance in contrast to reinforce concrete beam.Six SRCB have been done with different compressive strength of concrete,rebar ratio,rebar cover thickness and steel cover thickness. The paper analyses the character of deflection and crack development process in following aspects: the development of maximum width and average width of crack, the law between strain of rebar and steel with the width of crack and the crack closing character. Experimental study indicates that the deflection and crack development can be devided into three stages. SRCB with reasonable rebar and H-section steel arrangement manner has excellent serviceable performance,such as deflection, resistance to crack, crack width and crack closing performance.

Abstract: The uniform ZnO microsphere particles with a diameter of 390nm were synthesized by two-step method (also named seed solution method) projected by Eric W. Seelig. The chemical reaction details in the container were analyzed and the generation mechanism of ZnO microsphere particles was studied. ZnO films were prepared by vertical deposition. Coagulation phenomena occurred during the reaction process. The reaction conditions of coagulation phenomena were summarized and given reasonably explanations.

Abstract: Different content of sodium phosphate was added into the hemihydrates sulphate whiskers for 30 min to 2h of standing time. The treated products were researched by SEM, TG-DSC and XRD. The results indicate that when the dosage of sodium phosphate was more than 0.10%, the morphology of hemihydrate calcium sulphate whisker was fully maintained. However, the crystal structure of the products had changed and the half water calcium sulfate turned into of dihydrate calcium sulphate when 0.10 wt% sodium phosphate added. With the increase of standing time, half water calcium sulfate whisker converted into dihydrate calcium sulphate whisker. Sodium phosphate could reduce hydration ability of half water calcium sulfate whisker when the content of sodium phosphate was more than 0.10%.

Abstract: The hydration ability of CaSO₄ whiskers calcined under the condition of 475-500 °C for 10-60 min was researched by X-ray diffraction and scanning electron microscope. The optimal calcined CaSO₄ whiskers were added into building gypsum and the bending strength of gypsum board was influenced by different dispersion methods. The results show that the whiskers calcined under 475 °C for 30 min begin to hydrate and the aspect ratio of whisker calcined under 500 °C and 525 °C has no changed for 1 h of hydration time. The bending strength value of gypsum board with ultrasonic dispersed whisker is lower than that of gypsum board with directly mixed whisker.

Abstract: This paper studied the effect of polycarboxylate superplasticizer on cement hydration products through XRD, DTA/TG, ESEM, IR, XPS and adsorption test, and suggested that the new hydration products were not discovered in the adding PC sample; the adding of PC delayed the formation of hydration product of Aft; with the hydration, the PC molecules were wrapped by hydration products. Key word: polycarboxylate superplasticizer; cement; mechanism; hydration; hydration products

Abstract: Compared with other strengthening methods, NSM FRP bars strengthening method has obvious advantages in bond property and fire prevention performance. In accordance with current experimental study and the theory of concrete beams strengthened in bending with FRP are introduced, and the effect of FRP bars strengthening quantity on failure modes of reinforcement beams and the initial load level influence on the ultimate bearing capacity are analyzed. It provides a basis for further research and application in China.